1. Field of the Invention
The present invention relates to power equipment, including but not limited to mowers, tillers, snow blowers, and tractors, and more particularly, to a variable speed transmission and method for using the variable speed transmission.
2. Discussion of Related Art
Conventional power equipment such as lawn mowers, snow blowers, mulchers, etc. often include xe2x80x9cself-propulsionxe2x80x9d mechanisms for automatically driving the wheel, track or other drive mechanism used to propel the power equipment. Typically, the self-propulsion drive mechanism is activated by engaging a transmission that connects/disconnects the transmission shaft to the drive wheel. The speed of the drive wheel varies proportionally with the speed of the engine. Accordingly, the speed of the drive wheel can only be varied by changing the throttle position or by changing the gear ratios inside the transmission to increase/decrease the speed of the engine.
Recently it has become desirable to provide all types of power equipment with variable speed transmissions in order to smoothly vary the drive speed of the power equipment without increasing/decreasing engine speed to vary the drive speed. One attempt at providing such a device is currently incorporated in power equipment produced and sold in Europe by France Reductor, Inc. Idler pulley systems have also been used in an attempt to provide variable speed power equipment.
The France Reductor VST includes a first belt that is attached between a drive pulley on the engine output shaft and a driven pulley on a rotational shaft. A second pulley is attached to the same rotational shaft as the driven pulley and is locked and rotates synchronously with the driven pulley. A second belt is attached between the second pulley and a second driven pulley connected to a transmission shaft. The transmission shaft is connected to a transmission that transmits rotational power to a drive wheel or other drive mechanism. A clutch located in this transmission can be actuated to engage/disengage the transmission and transmit/disengage rotational power to the drive mechanism.
In order to vary the speed of the drive mechanism, a plate supporting the rotational shaft can be moved against the bias of a spring to tension and loosen the first belt and second belt, respectively. The first driven pulley and the second drive pulley (both of which are located on the same rotational shaft) have variable width grooves that are caused to vary when their respective belts are tensioned and loosened. Accordingly, when the first belt is tensioned, the first belt moves deeper into the groove of the first pulley towards the rotational axis of the rotational shaft, thus rotating the rotational shaft at ever increasing speeds as tension in the belt increases. Likewise, when the second belt is simultaneously loosened, the groove in the second drive pulley becomes narrower and the second belt moves out of the groove and away from the rotational axis of the rotational shaft, thus increasing the speed of the second belt and ultimately increasing the speed of the drive mechanism. Two belts are required in such a system to provide the necessary increase in variable speed output for the power equipment drive mechanism. In addition, two control mechanisms are necessary such that one control mechanism can actuate the transmission and one control mechanism can vary the speed of the transmission.
Because the France Reductor VST system requires two belts, four pulleys, two control mechanisms and a separate clutched transmission, the cost of the system and the space requirements are both relatively high. It is usually necessary to mount this VST system on top of a housing structure in order to fit such a large system on power equipment. In addition, the many different parts make the system susceptible to mechanical failures and creates problems with the range of aesthetic design available to power equipment that incorporates such a system. Furthermore, the actuation of the system is a two step process, and speed variation can be sudden at times if the transmission and the variable speed actuation mechanisms are not actuated in the correct order. The belts are also constantly moving in this related art VST system.
Another type of VST system that is commonly used in power equipment includes a hydrostatic transmission for varying the speed output to a drive unit. In such a system, a single control mechanism can be used to vary the speed of a drive unit from a neutral position to maximum speed. However, such transmissions are relatively expensive to manufacture. In addition, maintenance and repair of such a system are significantly more difficult and expensive than maintenance and repair of belt drive and/or geared transmission systems.
Accordingly, the present invention is directed to a variable speed transmission that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an efficient, inexpensive and compact variable speed transmission that can be actuated from a neutral position through a full speed position by a single actuator mechanism.
Another object of the invention is to incorporate the belt into the clutch mechanism of the variable speed transmission.
A further object of the invention is to provide a compact single actuation variable speed transmission that is capable of producing a relatively high level of output speed;
Another object of the present invention is to provide a compact assembly that can be easily and adequately shielded and requires as few parts as possible.
A still further object of the present invention is to minimize the number of pulleys and belts necessary, and to provide a variable speed transmission that uses a single belt connected between two pulleys such that the amount of moving parts is reduced and the possibility of malfunctions are reduced.
An additional object of the invention is to provide a control mechanism that varies drive speed between a neutral, intermediate and full speed position while also being variably operable between these three separate positions.
Another object of the invention is to vary the speed of a drive mechanism for power equipment in a smooth and reliable manner.
A still further object of the invention is to provide a compact single actuator mechanism that controls the output speed to a drive mechanism from zero to a maximum speed by moving the actuator mechanism in a single uniform motion.
Another object of the invention is to incorporate the variable speed transmission into the drive shaft of a motor such that a compact arrangement of the transmission can be achieved.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a variable speed transmission includes: a first pulley having a rotational axis and including a first face and a second face, the first face being movable with respect to the second face; a belt located adjacent the first face and the second face of the first pulley; and an actuator located adjacent the first pulley and adapted to move the first face to move with respect to the second face between a neutral position, an intermediate position and a full speed position, the neutral position defined by the first face being located at a first position with respect to the second face, and the first face being rotatable relative to the second face, the intermediate position defined by the first face being located at a second position that is closer to the second face than when the first face is located at the first position, the belt being in frictional engagement with the first face and second face such that motion of one of the first face, second face and belt causes another one of the first face, second face and belt to move, and the full speed position defined by the first face being located at a third position that is closer to the second face than when the first face is located at the second position, the belt being located in a position further from the rotational axis of the first pulley than when the first face is located at the second position.
The invention also includes a variable speed transmission for continuously varying the output speed of a drive wheel from zero to an upper speed limit, which includes: a single control mechanism capable of controlling the speed of the drive wheel from zero to the upper speed limit; an actuator connected to the control mechanism; and a drive train operationally connected between the control mechanism and the drive wheel, wherein the drive train includes a first and second pulley and no more than one belt.
In addition, the invention includes a variable speed transmission for continuously varying the output speed of a drive wheel from zero to an upper speed limit, which includes: a single control mechanism capable of controlling the speed of the drive wheel from the upper speed limit to zero; an actuator connected to the control mechanism; and a drive train operationally connected between the control mechanism and the drive wheel, wherein the drive train includes a first and second pulley connected by a belt, the first pulley having a rotational axis, a first face and a second face, the first face being movable with respect to the second face; wherein the actuator is located adjacent the first pulley and capable of causing the first face to move with respect to the second face between a neutral position, an intermediate position and a full speed position, the neutral position defined by the first face being located at a first position with respect to the second face, and rotatable with respect to the first face, the intermediate position defined by the first face being located at a second position that is closer to the second face than when the first face is located at the first position, the belt being in frictional engagement with the first face and second face such that motion of one of the first face, second face and belt causes another one of the first face, second face and belt to move, and the full speed position defined by the first face being located at a third position that is closer to the second face than when the first face is located at the second position, the belt being located in a position further from the rotational axis of the first pulley than when the first face and second face are in the intermediate position.
Furthermore, the invention can include a variable speed transmission, that includes: a first pulley having a rotational axis and including a first face and a second face, the first face being movable with respect to the second face; a second pulley having a second pulley rotational axis and including a primary face and a secondary face; a belt located on the first pulley and second pulley; and an actuator located adjacent the first pulley and adapted to move the first face with respect to the second face between a neutral position and a drive position, the neutral position is defined by the first face being located at a first position with respect to the second face, and the first face being rotatable with respect to the second face, the drive position is defined by the first face and second face being frictionally engaged with the belt such that the first face, second face and belt rotate together.
The invention can also include a variable speed transmission, including: a first pulley having a rotational axis and including a first face and a second face, the first face being movable with respect to the second face; a second pulley having a second pulley rotational axis and including a primary face and a secondary face, the primary face being movable with respect to the secondary face along the second pulley rotational axis; a biasing mechanism located adjacent one of the primary face and secondary face of the second pulley and adapted to bias the primary face towards the secondary face; a belt located on the first pulley and second pulley; and an actuator located adjacent the first pulley and adapted to move the first face with respect to the second face between a neutral position and a drive position, the neutral position is defined by the first face being located at a first position with respect to the second face, and the first face being rotatable with respect to the second face, the drive position is defined by the first face and second face being frictionally engaged with the belt such that the first face, second face and belt rotate together.
Additionally, the invention can include a method for using a variable speed transmission that includes a first pulley having a rotational axis, a first face and a second face, the first face being movable along the rotational axis with respect to the second face, a belt located adjacent the first face and the second face of the first pulley, the method including driving one of the first face, the second face and the belt about the rotational axis of the first pulley; moving the first face along the rotational axis and relative to the second face such that a portion of each of the first face and the second face frictionally engages the belt to cause one of the first face, the second face and the belt to begin movement about the rotational axis of the first pulley; and moving the belt away from the rotational axis of the first pulley to cause the belt to move faster about the rotational axis of the first pulley.
The invention can also include a method for using a variable speed transmission that includes a first pulley having a rotational axis, a first face and a second face, the first face being movable along the rotational axis with respect to the second face, a second pulley having a second pulley rotational axis, a primary face and a secondary face, the primary face being movable with respect to the secondary face along the second pulley rotational axis, a belt connected between the first pulley and the second pulley, including: driving one of the first face, the second face and the belt about the rotational axis of the first pulley; moving the first face along the rotational axis and relative to the second face such that a portion of each of the first face and the second face frictionally releases from the belt to cause one of the first face, the second face and the belt to begin movement relative to another one of the first face, the second face and the belt.
The invention can also include a method for using a variable speed transmission to drive a propulsion mechanism on a piece of power equipment, including: providing a control mechanism that is connected to a drive train which drives the propulsion mechanism, the drive train including a first pulley having a rotational axis, a first sheave and a second sheave, and a belt having an inner surface located around the first pulley; permitting the first sheave to remain substantially stationary relative to the second sheave; rotating the first sheave of the first pulley with respect to the belt; and engaging the belt with the first sheave of the first pulley with enough force to begin movement of the belt about the first pulley.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.